Huan Liu

Self-collisions of a dual-arm robot system can cause severe damage to the robot. To deal with this problem, this paper presents a real-time algorithm for preventing self-collisions in dual-arm systems. Our first contribution in this work is a novel collision model built using discrete spherical bounding volumes with different radii. In addition, we propose a sensitivity index to measure the distance between spheres with different radii in real time. Next, according to the minimal sensitivity index between different spheres, the repulsive velocity is produced at the centers of the spheres (control points), which the robot uses to generate new motion based on the robot kinematic model. The proposed algorithm offers the additional benefits of a decrease in the number of bounding spheres, and a simple collision model that can effectively decrease the computational cost of the process. To demonstrate the validity of the algorithm, we performed simulations and experiments by an upper-body humanoid robot. Although the repulsive velocity acted on the control points, the results indicate that the algorithm can effectively achieve self-collision avoidance by using a simple collision model.

Restoring human grasp functions by prosthesis is a long-standing challenge in robotics research. Aiming at prosthetic applications, this paper presents a novel anthropomorphic multi-grasp hand design. The hand is driven by only one motor, and several mechanisms were designed for enhanced functionality. First, a continuum differential mechanism (CDM) was used to generate differential finger motions and to simplify the transmission of the hand. Second, a load adaptive variable transmission (LAVT) was designed to magnify the grasp forces. Moreover, a prismatic clutch is embedded in the hand, to lower the motor's energy consumption. Myoelectric control was implemented using affordable control hardware and sensors. All the above components are integrated in the proposed prosthetic hand, which is an average adult male size and weighs 470 g (including batteries). Experiments, including a preliminary clinical evaluation, were conducted to assess the effectiveness of the hand for prosthetic use. The results show that the hand can perform various grasps and can be a viable option for transradial prosthesis.

Recently underactuated robotic hands has been exploited for dexterous in-hand manipulation, after been proven efficient in performing versatile adaptive grasps. However the in-hand manipulation reported are usually associated with parasitic motion, which may complicate the control and application of the hand. This paper presents the modeling, optimization and experimentation of the ParaGripper, which is an underactuated gripper capable of performing in-hand manipulation without parasitic rotation. The underactuated finger uses two serially connected parallelograms to ensure pure translation of the fingertips. If the object remains stationary to the fingertips, the gripper can translate the object without parasitic rotation. The kinematics and kinetostatics of the hand-object system are derived and the manipulation workspace is optimized. The ParaGripper is designed and fabricated according to the optimal parameters. Experiments showed that the ParaGripper could perform non-parasitic in-hand manipulation and versatile adaptive grasps.